Attempts have been made in the past to utilize laser or light gauges to determine two mutually perpendicular cross-sectional dimensions of an elongated workpiece, for example, as shown in U.S. Pat. No. 3,870,890. The laser beam is projected onto a rotating mirror and then a long path to the object is folded by mirrors to provide a smaller physical size of gauge. The beams are spread out by mirrors into two separate paths, and then passed through lenses to establish substantially parallel laser beams which scan across the object in two mutually perpendicular directions. The laser beams then pass through two additional lenses and a long path length is folded by additional mirrors to impinge on two separate photocells. The time of scanning across a workpiece is measured and the first and second dimensions are determined from such first and second scanning times.
U.S. Pat. No. 3,461,299 utilizes four plane mirrors and a light source illuminating an object with a photocell covered by an enclosure having a slit and the enclosure rotates to be illuminated by a light beam directly past the object or reflected off the mirrors. Such system is alleged to be sensitive enough to detect the difference between one object and two objects.
U.S. Pat. No. 3,787,700 has two linear arrays to scan the diameter of a log along two dimensions perpendicular to each other and using a lens system together with an accurately known distance between the linear arrays and the object to be measured.
U.S. Pat. No. 3,997,269 shows measurement of the diameter of a log along two dimensions perpendicular to each other. Each measurement is made by a separate parabolic mirror and the time for a scan across the diameter of the log is determined by a clock frequency. This clock frequency is varied in a step fashion or, alternatively, is infinitely varied by a cam in order to correct for the inherent nonlinearity caused by the parabolic mirror.
U.S. Pat. No. 4,201,476 shows a laser dimension gauge capable of determining a single dimension of a given cross section of a bar workpiece, and utilizing a parabolic mirror and retroreflective surface.